The research plan described in ths application will conduct two Phase II randomized, placebo-controlled trials, each of which compares two active medications to a common placebo condition as treatments for methamphetamine abuse. The design innovation allows 4 medications to be tested using a total of 240 participants (120 per trial). The trials involve a 2-week baseline period followed by randomization to 12 weeks of medication. In the first trial, participants will be randomly assigned to receive aripiprazole (10mg qd;n=35), rivastigmine (1.5mg bid;n=35), or placebo (matched in appearance;n=50) as relapse prevention agents. Contingency management will be initiated during baseline and continued through the fourth week of medication to instill significant periods of abstinence. Cognitive behavioral therapy will be provided during the entire trial period to teach skills for avoiding relapse. This project will determine whether any of the tested medications have sufficient efficacy and safety to devote resources for full-scale definitive trials. The Specific Aims of these Phase II trials are: (1) to determine whether an active medication compared to placebo reduces drug use (urine drug screens;self-report) among treatment-seeking participants with methamphetamine abuse or dependence;(2) to determine whether an active medication compared to placebo retains participants in treatment longer than placebo;(3) to determine whether an active medication sompared to placebo reduces craving (VAS) for methamphetamine;(4) to assess the ability of an active medication compared to placebo to reduce somatic complaints (BSI), demonstrate acceptable levels of safety (AE reports), improve emotional functioning (BDI-II, QWB), and improve overall clinical improvement (CGI);and (5) to assess the ability of an active medication compared to placebo to reduce HIV-related transmission behaviors (RAB). This P50 renewal will continue our tradition of refining and extending technological expertise in the conduct of medication development for stimulant abuse and dependence.